This invention relates to the moistening of whole grains, more particularly to a novel method of effecting such moistening and to an apparatus for carrying out the method.
The invention is applicable to whole grains of all types, and is especially advantageous when used in conjunction with whole cereal grains, such as for example wheat, barley, oats, millet, rice and the like.
Cereal grains find their largest use as flour. Before they can undergo conversion into flour in a flour mill they must be subjected to several preliminary processing operations, since they cannot be supplied to the flour mill in the condition in which they are harvested. The most important of these preliminary operations is the cleaning of the grains. This is carried out in the prior art in one of two ways: The cereal grains, and to be more specific the kernels of cereal grain, are either washed in special washing machines provided for this purpose or they are washed in so-called wet scrubbers. If the grains are washed in washing machines they will, at the end of the washing operation, have a moisture content that is increased by between 2 and 3% over the moisture content prior to the washing operation. If they are cleaned in a wet scrubber, then the moisture content increase will be between 1 and 1.5%. It will be appreciated that in neither case it is possible to predetermine the exact amount of moisture increase in the kernels.
This is found highly disadvantageous because flour milling requires that the kernels being ground have a specified moisture content which is allowed to vary only within very narrow limits. This moisture content is higher than that which can be imparted by either of the two washing methods, and therefore the kernels have water added to them subsequent to the washing operation. Particularly in the case of grain which has been cleaned according to still a third method, namely the dry cleaning method which does not involve the use of water, the moisture content of the cereal must often be increased by 5-6%. This adjusting of the moisture content is of great importance in the milling industry, because the moisture content of the grain strongly influences the subsequent operations, such as grinding, sifting and the like.
The moisture content must, however, not only be increased to a certain value, but it must also be as uniform as possible. According to the prior art it is known to admit a stream of the grain kernels into a trough in which a slowly rotating conveyor screw or blade-conveyor screw is mounted, and into which water is admitted, so that the grain kernels are carefully and uniformly turned over in the water. Subsequently, the wetted grain kernels are admitted into a receptacle in which they are allowed to sit for a prolonged period of time, the intention being that the water which adheres to the surface of the kernels is to penetrate into their interior to thus soften the kernels and in particular the outer coat of the kernels which hopefully should become somewhat elastic.
Different types of grains react differently to this prior-art moistening. For example, certain types of grain kernels, such as wheat, have a pronounced depression in their exterior surface, whereas others -- such as rice and millet -- do not have such a depression. The surface area in which the depression is formed, amounts to a significant percentage of the total surface area of the particular kernel. It was found that during the initial wetting operation in the prior art the wetting liquid would enter into such depressions only to a limited extent, and that the area of the germ of the particular kernel also became wetted only to a limited extent. In part this was made up by the subsequent soaking, that is the penetration of the liquid into the kernels when the latter were allowed to rest after the wetting operation. However, uniformity of wetting and soaking could never be achieved. This is known in the industry to be highly disadvantageous; for example, it is well known that a non-uniform wetting of the kernels of one and the same type of wheat is very disadvantageous for subsequent operations, and that it is of course more disadvantageous if a mixture of different types of grains is non-uniformly wetted and moistened.